Impact of liquid microbial inoculants of Azotobacter sp. and Stenotrophomonas maltophilia on soil fertility and productivity-cum-economics of cluster beans

ABSTRACT Liquid microbial inoculants (LMIs) can play a paramount role in integrated nutrient management as these are renewable and eco-friendly sources of plant nutrition. Here, we evaluated the impact of LMIs, such as of Stenotrophomonas maltophilia and Azotobacter sp., on the growth and yield parameters of cluster bean (Cyamopsis tetragonoloba (L.) Taub.). The bacterial culture, S. maltophilia, was isolated from the nodules of cluster bean and identified by sequencing the 16SrRNA gene. On applying LMIs and 75% recommended dose of fertilizer (RDF) (T7), a significant improvement in plant height, dry fodder yield and seed yield was observed. Besides, there was a ~ 10% increase in all the other growth and yield attributes, such as no. of branches, no. of pods, pod length, no. of grains per pod, and 1000-grain weight. The increase in seed yield and dry fodder yield with T7 over the T1 (RDF) was 16% and 19%, respectively. Moreover, the total energy output of different treatments as computed from the main products ranged from 69,973.5 to 82,490.1 MJha−1. This might be due to higher seed and dry fodder yield with LMIs. The different LMI treatments increased the net returns of cluster beans over the control (T7, US$ 527.91). The soil analysis revealed the improvement in macro (N, P and K) and micronutrients (Fe, Cu, Zn and Mn) by 10–20% after the LMI treatments. Thus, priming seeds with LMIs could be an effective strategy to stimulate the growth of cluster beans without compromising the soil fertility.